This invention relates to cardiac monitors and more particularly to a telemetry cardiac monitoring system.
During critical phases of cardiac illness, it is necessary to monitor a patient's physiological data, such as, heart rate, arrhythmia, the frequency of pacemaker pulses and ECG signals. In one type of patient telemetry monitoring system, a number of patients are monitored simultaneously at a central station. Such systems must provide the medical staff with continuous and reliable patient data and generally include a plurality of remote patient monitors and a central station unit coupled to the remote units by a wired data bus or by a radio frequency transmitter and receiver. If a radio system is employed, it is desirable that interference and sudden dropout be minimized. In addition, the system must not only alert the medical staff to sudden changes in the patient condition, but also partial or total system failures. Also, because telemetry nursing staffs operate under a substantial work load and the critical nature of a patient's condition, such systems now must provide accurate heart rate and arrhythmia detection in addition to continuous patient surveillance.
To provide the medical staff with usable accurate patient data, the telemetry system must first transmit and receive patient ECG data continuously and reliably. Currently available systems are not wholly satisfactory because they are prone to signal fade and drop out plus multipath distortion.
Another shortcoming of prior art telemetry systems is that only a single lead or vector of ECG data is transmitted for analysis and display. Because this limits the amount of ECG data which is processed, there is a greater tendency for incorrect classifications and false alarm. A further limitation of prior art systems is that lead failure or low battery conditions can only be determined at the central station and not at each patient location.